Many drugs, particularly those used in treatment of various eye disorders, are administered in drop form. The drops of liquid are intended to free-fall onto the eye surface, where it is distributed across the exposed eye. Dosage of these ophthalmic drugs is often crucial. For example, lower than prescribed levels of the drugs can result in failure of treatment and consequent progression of the disease and higher levels can result in intractable side effects which can also interfere with successful resolution.
Complicating the administration of these drugs is the fact that they are often required several times a day and thus to be practical, must be administered by the patient rather than medical personnel who are formally trained in drug delivery. Patient administration of such drugs has resulted in two serious problems, namely, bottle contamination and flow rate which must be solved for medications to be successfully administered.
Container devices having multiple compartments for separately enclosed materials to be mixed prior to use are described in U.S. Pat. Nos. 3,340,873; 3,354,883; 3,397,694; 3,411,503; 4,331,146; 4,412,836; and 4,330,531, having a thin diaphrame-type membrane separating the two compartments. These systems are not considered entirely reliable due to its ability to maintain a fluid-tight seal between the compartments. U.S. Pat. No. 3,464,414 discloses a rigid walled two chambered mixing vial utilizing hydraulic pressure to dislodge a plug member between the two chambers.